


Null Spaces

by hyliank8



Category: Undertale (Video Game)
Genre: Established Sanster, Fluff, Happy Ending Sanster, Implied Sexual Content, M/M, Post-Accident W. D. Gaster, Post-Undertale Pacifist Route, Sexual Tension, Tactile Fixation, W. D. Gaster is not related to Skelebros, but no actual sex, i sure as hell can't, it's gonna be on gaster's desk again tho obviously, sexual fantasies, they're happy i did it i wrote a fic where they're both happy can you believe it???
Language: English
Status: Completed
Published: 2020-06-04
Updated: 2020-06-04
Packaged: 2021-03-04 00:34:39
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 991
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24534700
Author URL: https://archiveofourown.org/users/hyliank8/pseuds/hyliank8
Summary: Gaster has been saved from the void and spends his days with Sans happily working in their new lab on the surface.Gaster missed Sans in more ways than one.(happy belated 06/03 sanster day!)
Relationships: W. D. Gaster/Sans
Comments: 14
Kudos: 89





	Null Spaces

**Author's Note:**

> they're HAPPY this is not a drill i repeat they are HAPPY (and thirsty af for each other but like what else is new)
> 
> hi this was for sanster day (06/03) but it's late cause i'm taking 24 course credit hours and i'm super burnt out :( but i wanted a lil break so i wrote this!!! also it's technically not porn this time wow amazing

It’s late afternoon, nearing the end of Sans’ workday at Gaster’s labs. After monsterkind reached the surface, Asgore managed to convince the human leadership of the importance of progressing in the field of monster science, successfully securing Gaster and his team a space to work on the surface in the process. Sans can’t help but miss the old labs a bit, if only for nostalgia’s sake; still, he has to admit the sunlight peeking in through the windows of his new environment is a nice touch—a reminder of how far they’ve all come after working so hard.

And then there’s the impossibly wonderful feeling of having Gaster back with him after all of this time, too. So many years passed by without him—years of yearning, of tireless work on the machine for just a chance at getting his partner back, years of Sans hopelessly trudging through his monotonous daily life because there was no other choice—but now Gaster is back working alongside Sans in the labs, pioneering the fields of magic science just like old times.

It’s clear that Gaster is just as delighted to be back as Sans is to have him back, if not more so. When Sans observes the way the scientist moves around the lab checking his observations, he notices a bounce in his step that he didn’t use to see in the Underground. Gaster’s told him stories about the horrors of the void—the complete lack of sensation and autonomy, the uncertainty of one’s own existence, the neverending emptiness—and Sans can only imagine the juxtaposition between that null space and the surface world they inhabit now. To return to a tangible world after so long surviving an endless state of unfeeling, and for that world to be on the surface, the place Gaster and his team had worked tirelessly to reach for decades—well, that certainly warrants the scientist’s excess energy; Sans suspects it’s an enthusiasm for the everyday experiences of life born from the anguish of existing without them for so long.

Touch, in particular, was apparently one of the things Gaster missed most. He told Sans of the mock eternity he spent longing to hold Sans’ hands in his own, the times he would think of his partner and nothing else. Some of the thoughts were rather… _explicit_ at times, too, but Gaster was happy to fill Sans in; he recounted his desires shamelessly, in enough detail and with enough passion that Sans couldn’t stop the heat that rushed to his cheekbones.

Sans notices Gaster’s touch lingering longer these days, finding excuses to have contact with him whenever he can, and Sans has come to enjoy Gaster’s diminishing concept of personal space.

That said, it’s a bit difficult to get work done when Gaster _insists_ on fulfilling his sensory needs in the middle of the day.

“wings, c’mon,” Sans sighs.

He’s trying to get work done at his work station in the labs, but it’s a little bit difficult with his fiancé “checking up on him” all the time, and being so… _tactile_ about it. He can hardly go a few hours working without Gaster coming by his work station—usually when no one else is around—and giving him a particularly amorous hug from behind. 

Somewhere along those lines Gaster managed to work his hands underneath Sans’ shirt; now he rests his palms lightly on the front of Sans’ ribs as he holds his small assistant close, tracing delicate patterns into his sternum. “What is it, Sans?” he murmurs. His hot breath on the back of Sans’ neck sends small, heated shivers down the short skeleton’s spine. “Is something amiss?”

“you _know_ i can’t focus with you doing stuff like this all the time,” Sans protests.

“Mm, ‘stuff’ like… what, exactly?” Gaster shifts his hand to the edge of Sans’ ribcage. Sans’ breath catches, a heat quickly budding in his soul.

“i—… you know what you’re doing,” Sans mutters.  
  
“I’m simply trying to make sure you’re doing alright,” Gaster murmurs lowly. “My dearest lab assistant is crucial to ensuring smooth operations around here; you could imagine how much stock I put in your personal well-being…” As he speaks, his hands trail around the edges of his lowest ribs and then move lower—down his spine slowly, tantalizingly—to rest on his iliac crests. 

“If there’s anything you need, you know… all you must do is ask. I have plenty of… _resources,_ at my disposal.” Sans gasps as he feels an unexpected tug on his ribs, heat flaring within him as he realizes Gaster materialized two extra hands to hook his fingers between his ribs. The fingers push further into the void between his bones and Sans can’t help the whimper that the intimate touch pulls out of him. 

Gaster brushes his lips against the top of Sans’ skull, and that warm, soft sensation simmering alongside the demanding touch of Gaster’s magic ignites a fire in Sans’ soul that can no longer be ignored. God, Sans wants, _needs_ more of that touch; he craves the roughness of those hands hungrily exploring every inch of his body, holding him still as he writhes from Gaster’s eager attention—

“god, i—dammit, ‘dings!” Resolve snapped, Sans spins around and grabs Gaster by the collar, shortcutting them to Gaster’s private office. He lands them squarely in front of Gaster’s desk, Sans’ spine pressed up against the edge of it as he uses his grip on Gaster’s shirt to yank his partner down to his height.

“just—just _fuck_ me already,” he gasps against his lover’s lips.

“Gladly,” the doctor breathes, soul already thrumming with arousal. He effortlessly lifts his partner up onto the desk, sliding easily between his knees. He has just enough thought left to conjure a magic hand to flip the lock on the door across the room, giving them plenty of privacy as he pushes his assistant down against the desk.

**Author's Note:**

> HI thank u for reading i hope u enjoyed the happiness for now bc um (hides my 5 current wips) ...i mean, no reason
> 
> forreal tho do u kno how hard it was for me Not to give gaster explicit heart-wrenching trauma from being trapped in the void :flushed emoji: ...harder than it should have been, probably,
> 
> if u wanna see me elsewhere i'm mainly on [twitter (nsfw)](https://twitter.com/K8Maybe) these days, but also [tumblr (mostly sfw!)](https://hyliantimelordin221b.tumblr.com)
> 
> also okay i have the sanster url on tumblr now so [feel free to follow me on tumblr there](https://sanster.tumblr.com) if u would like as well lool
> 
> feel free to leave a comment ^^


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